A typical form measuring machine that measures a form of an object using a scanning probe has been known. When the form measuring machine performs, for instance, a circle measurement using the scanning probe, a motion error in the form of a projection (i.e., quadrant projection) is inevitable in switching quadrants in a machine rectangular coordinate system (i.e., inverting a motion direction in each axis), which results in a measurement error.
In view of the above, form measuring machines configured to correct a measurement error due to the quadrant projection are disclosed (see, for instance, Patent Literature 1: JP-A-2007-315897, Patent Literature 2: JP-A-2014-66693 and Patent Literature 3: JP-A-2014-98610).
The machine of Patent Literature 1 uses a correction filter designed in view of characteristics of frequency transfer from a scale to a slider tip to correct a measurement error due to the quadrant projection. In order to correct a measurement error due to the quadrant projection, the machine of Patent Literature 2 uses a correction filter designed in view of characteristics of frequency transfer from a scale to a probe tip ball, and the machine of Patent Literature 3 uses a correction filter designed in view of inverse characteristics of frequency transfer from a scale to a probe tip ball.
According to Patent Literatures 2 and 3, a correction factor suitable for the scanning probe is applied to the correction filter in advance to correct a measurement error due to the quadrant projection. However, when a stylus of the scanning probe is replaced, the correction filter cannot sufficiently exhibit a correction performance, which necessitates a troublesome work. For instance, an operator needs to input a correction factor suitable for the scanning probe attached with a new stylus so that the correction filter can sufficiently exhibit a correction performance.